Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders. Chronic stress is associated with the onset and exacerbation of symptoms in IBS and female sex is a risk factor for this detrimental stress effect. Perturbations during the pre- and perinatal period or childhood may contribute to the development of IBS in adults. Early life stress is associated with a dysregulated hypothalamic-pituitary-adrenal (HPA) axis. IBS patients report an increased prevalence of early life stress and demonstrate increased HPA axis activity. Our preliminary data shows increased methylation of the glucocorticoid receptor (GR) NR3C1 promoter in IBS patients but none in controls. This finding may be associated with decreased negative feedback of glucocorticoids and HPA axis hyperreactivity in IBS. Rodents exposed to perinatal stress (i.e., maternal separation, [MS]) are predisposed as adult rats to develop stress-induced visceral hypersensitivity, enhanced defecation, intestinal mucosal dysfunction, increased HPA axis responses and anxiety-like behavior and these responses are mediated by activation of corticotropin releasing factor receptor 1 (CRF-R1) signaling pathways. These phenotypic features are homologous to those seen in IBS patients and thus, the MS animal model is a relevant model of IBS. Project 1 focuses on the identification of a biological marker for IBS and associated alterations in the stress response systems, and on a translational approach in rodents to identify alterations in CRF-R1 signaling and GR promoter methylation in specific brain regions and circuitries following early life stress. Aim A's objective is to conduct a comprehensive genetic, molecular and functional phenotyping of HPA axis in male and female patients with IBS, IC/PBS and controls. Aim B proposes to establish that perinatal stress (MS) alters the pattern of regional brain CRF and CRF-R1 expression, and DNA methylation of GR promoter region in male and female rats. Aim C intends to delineate the increased engagement of central stress responsiveness/arousal mechanisms in the rat MS model with an emphasis on identifying homologies of rodent brain imaging with human findings from Project 3.